(1) Field of the Invention
The invention relates to a rescue structure and a method for laser welding, and more particularly to the one that can improve the rescue quality by simplifying the needed rescue process.
(2) Description of the Prior Art
It is well known that the display area of the liquid crystal display (LCD) is formed by crossing a plurality of data lines with a plurality of gate lines. A pixel of the display area is the square area defined by two adjacent data lines and two adjacent gate lines. By providing transistors internally to the pixels and by controlling illumination of the transistors, a predetermined image can thus be displayed.
Referring now to FIG. 1, a schematic view of a typical conventional LCD is shown. The LCD 1 includes a glass substrate 10 having a middle display area formed by intersecting a plurality of data lines and a plurality of gate lines. In the art, the signal line 2 of the LCD 1 can be the data line or the gate line. Yet to simplify the description herein, the signal line 2 is assigned to the data line. A plurality of driver integrated circuits (IC) 3 are located to the rim of the glass substrate 10. Each of the driver ICs 3 is used to control signal flow of one or more than one signal lines 2. A circuit board 4 is located outside the glass substrate 10 for electrically connecting the driver ICs 3 and some external power sources.
Empirically, in the manufacturing process of the signal lines 2, possible particle contamination to break the line is also possible, as area C shown in FIG. 1. As long as the situation of such contamination to break the signal line happens, a repair upon the broken signal line 2 is required so as to activate the pixels located in the downstream of the signal line 2 after the area C.
In the art, to repair contamination in the signal lines, some rescue lines are usually included in the LCD 1, such as rescue lines R1 and R2 in FIG. 1. The rescue line R1 or R2, crossing the signal line in a projection wise, is located at a metal layer of the glass substrate 10 different to the layer that lies the signal lines 2. Generally, the rescue line R1 or R2 is constructed at the first metal layer M1, while the signal lines 2 are constructed at a second metal layer M2. The first metal layer M1 and the second metal layer M2 are separated by an isolation layer in between. As shown, the rescue line R1 or R2 is extended along the rim of the glass substrate 10, and, by passing through the pass inside the driver IC 3 and lines 5, 6 or 5a, 6a of the circuit board 4, connected to an end of the respective signal line 2.
For example, in the case that point P of the signal line 2 is a broken point and needs to be repaired, a typical repair is to engage by laser welding (1) the signal line 2 at area A with the rescue line R1 and (2) the signal line 2 of area B with the rescue line R1, and then signals of the driver IC 3 can be transmitted to the lower-P area of the line 2 via the rescue line R1. Upon such an arrangement, the display at pixels in the lower-P area of the line 2 can be resolved and thus the display quality of the LCD can be greatly improved. Note that the only defect pixel now is the pixel at point P.
Referring now to FIGS. 2A thru 2D, a conventional laser repairing to the area A of the signal line 2 in FIG. 1 is shown. To convene the laser welding, the intersection of the signal line 2 and the rescue line R1 is originally made to a broader welding pad 21. The welding pad 21 is formed by extending sideward the signal line 2 as shown in FIGS. 2A and 2B. When the laser welding is processed manually, the laser penetrates the welding pad 21 at weld points 8 to integrate metally the upper signal line 2 and the lower rescue line R1. To avoid additional loading resulted from signal transmission to the left side of the rescue line R1 and to reduce the resistance-capacity (RC) value of the LCD, an additional laser cutting 81 to cut the rescue line R1 left to the welding pad 21 is processed, as shown in FIGS. 2C and 2D.
As noted in the art, laser welding and laser cutting are repeated again and again to process the conventional laser rescue. In addition, while in manual laser welding, the welding pad is made broader to ease the manual laser operation. Yet, the increase of the RC value is the trade-off. As a consequence of the aforesaid laser rescue, the signal realization is substantially lowered and the yield of the rescue is also reduced.
Therefore, an improved laser rescue method to increase the rescue yield without sacrificing the RC value is needed.